## Article

```catala
declaration structure S:
  data x content integer
  data y content boolean

declaration structure T:
  data a content S
  data b content S

declaration scope A:
  context output t content T

declaration scope B:
  context output t content T
  a scope A
  context output out content integer

scope A:
  definition t equals T {
    -- a : S {
      -- x : 0
      -- y : false
    }
    -- b : S {
      -- x : 1
      -- y : true
    }
  }

scope B:
  definition t equals a.t
  definition out equals if t.a.y then t.a.x else (if t.b.y then t.b.x else 42)
```



```catala-test-inline
$ catala Typecheck --check-invariants
┌─[RESULT]─
│ All invariant checks passed
└─
┌─[RESULT]─
│ Typechecking successful!
└─
```

```catala-test-inline
$ catala test-scope A
┌─[RESULT]─
│ t = T { -- a: S { -- x: 0 -- y: false } -- b: S { -- x: 1 -- y: true } }
└─
```

```catala-test-inline
$ catala test-scope B
┌─[RESULT]─
│ out = 1
│ t = T { -- a: S { -- x: 0 -- y: false } -- b: S { -- x: 1 -- y: true } }
└─
```